Precise analysis of ICESat altimetry data and assessment of the hydrostatic equilibrium for subglacial Lake Vostok, East Antarctica

Abstract

SUMMARY Based on the Ice, Cloud and Land Elevation Satellite (ICESat) laser altimetry data, the hydrostatic equilibrium (HE) condition for the subglacial Lake Vostok, East Antarctica, is evaluated. A digital elevation model (DEM) of the ice surface is derived by a regional crossover adjustment. The analysis of the DEM and its comparison with GPS derived ice‐surface elevations and an ice‐surface DEM based on radar altimetry data reveal an overall accuracy of better than ± 0.7 m for the lake area. The DEM is combined with an ice‐thickness model and a regional geoid model to determine the deviation of the local ice‐surface height from HE. For large parts of the lake, the ice sheet fulfils the HE. Our results reveal a strong positive deviation of about 10 m along the lake shoreline. In addition, positive deviations are found in the northern part of the lake which coincide with ice rumples detected by radio‐echo sounding. In the southern part of the lake, we find a linear negative deviation (−4.0 m) which coincides with the convoy route from Vostok station to Mirny base. In addition to the DEM, relative biases for the ICESat laser operational periods are determined in the regional crossover adjustment.

An investigation of Glacial Isostatic Adjustment over the Amundsen Sea sector, West Antarctica

“…While the former are part of the GLAS-12 product, the latter were derived by a crossover minimisation approach over a stable region of the AIS (Lake Vostok) (Richter et al, 2008). These bias corrections prove to be in good agreement with other published results (Ewert et al, 2012b).…”

Comment on ‘Mass gains of the Antarctic ice sheet exceed losses’ by H. J. Zwally and others

“…Further, as presented by Ewert and others (2012), Subglacial Lake Vostok is in hydrostatic equilibrium, at least in its central ice surface area. This means that any valid ice-driven elevation change seen in the surrounding EAIS region should be reduced to ∼1/12 the grounded-ice rate over the lake surface.…”

“…The following is a partial list of web pages offering initial responses to the Zwally 2015 , grey left-corner triangles; "MH 86 13" (Hofton and others, 2013, 86°S ring), blue circles; "MH EA 13" (Hofton and others, 2013, East Antarctic divide), purple squares; "VH14" (Helm and others, 2014, Vostok area; modified from Ewert and others, 2012), red diamonds; "BG14" (Gunter and others, 2014, East Antarctic low precipitation zone), orange up-pointing triangles, "TU13" (Urban and others, 2013, global ocean) down-pointing blue triangles; and "AS12" (Shepherd and others, 2012, global ocean), uppointing blue triangles.…”

A range correction for ICESat and its potential impact on ice-sheet mass balance studies

“…There have been many independent estimates made of ICESat intercampaign biases (e.g., Siegfried et al, 2011;Zwally et al, 2011;Shepherd et al, 2012;Ewert et al, 2012;Gunter et al, 2013;Hofton et al, 2013), many of which were directly compared in Urban et al (2012). There is little consensus between estimates of individual biases or bias trends: the seven estimates considered in Urban et al (2012) yielded biases that differed by up to 20 cm for any single campaign and bias trends that ranged from −0.3 to +2.2 cm yr −1 over the L2a-L2f period.…”